Ferrite power divider



Sept. 4, 1962 J. CARTER ETAL FERRITE POWER DIVIDER Filed Dec. 22, 1961 FIG.3

TEOI AND T2 MODES IN VEN TOR S JOHN L cmran a consum noaznr A. MOORE.

MAGNET y FIELD TE MODE ATTORNEY United States Patent 3,052,856 FERRITE POWER DIVIDER John L. Carter, Ash-dry Park, N.J., and Robert A. Moore,

Severna Park, Md, assignors to the United States of America as represented by the Secretary of the Army Filed Dec. 22, 1961, Ser. No. 161,751 4 Claims. (Ci. 333-6) (Granted under Title 35, US. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment of any royalty thereon.

This application is a continuation-in-part of the application of John L. Carter and Robert A. Moore, Serial Number 70,361, filed November 18, 1960, for Mode Converter and Application Thereof.

The invention relates to the control of electromagnetic energy propagated over a waveguide transmission system and particularly to mode converters for use in said systems to elfectively produce a microwave power divider.

It is known that microwave electromagnetic energy can be propagated over a waveguide transmission system in a large number of distinctive transmission modes or characteristic electric field configurations dependent on the size and shape of the particular waveguides used and the operating frequency. For example, one of the modes which can be transmitted over a rectangular waveguide is the dominant mode, called the TE mode, which is that of the lowest critical cut-off frequency, characterized by an electric field which is oriented completely transverse to the direction of energy propagation with no amplitude variation along the narrow transverse dimension of the guide, and half-sinusoidal amplitude variation along its wide transverse dimension. The first higher order transverse mode which can be propagated over a rectangular waveguide, called the TE- mode, also has no amplitude variation along the narrow transverse dimension of the guide but has a full-sinusoidal amplitude variation along its wide transverse dimension.

It is known that certain materials, described by the mathematical analysis of D. Polder in Philosophical Magazine, vol. 40, pp. 99 through 115 (1949), exhibit certain anomalous attenuation characteristics which are not predicted by Polders theory. These materials, one of which is ferrite, are characterized by certain unpaired electron spins which respond to a transmitted microwave by precessing gyroscopically about the line of an applied magnetic field. The interaction of these precessing electron spins with the applied microwave result in certain magnetic properties which have given the name gyromagnetic to these materials. It is also known that when an electromagnetic wave is impressed in suitable manner upon such a material, which is magnetized to saturation along a fixed direction, its effective permeability can be varied over a wide range including positive and negative values by varying the strength of the steady magnetizing field, and thus the impedance of the wave impressed thereon and its propagation constant can be controlled over a correspondingly wide range.

The gyromagnetic properties of such materials have been utilized to control the propagation of electromagnetic waves over waveguide systems. For example, it is known to employ the gyromagnetic absorption associated with the Faraday rotation in ferromagnetic materials to convert a linearly polarized wave of electromagnetic wave energy into a circularly polarized component.

A general object of the invention is to utilize the gyromagnetic phenomena of ferrite or other gyromagnetic material to control the transmission mode or characteristic field configuration of electromagnetic wave energy propagated over a rectangular waveguide system in a desired manner.

Related objects are to utilize such gyromagnetic materials to provide power division or power limiting on electromagnetic energy propagated over rectangular waveguides.

Another object is to convert oscillations propagated over a rectangular waveguide in one transmission mode to oscillations in a diflerent mode, both modes being simultaneously propagated through the waveguide.

A more specific object is to utilize the gyromagnetic properties of ferrite or other gyromagnetic material to convert electric wave energy propagated through a rectangular waveguide in a fundamental mode to electric wave energy propagated through the same rectangular waveguide in the first higher order transmission mode.

In accordance with the invention,'conversion between two orthogonal electromagnetic transmission modes, for example, between the TE and the TE modes, is efiected in a rectangular waveguide system by the inclusion therein of an element which couples with both of the modes. The mutual coupling element may be a slab or rod of ferrite or other semiconducting or insulating material having gyromagnetic properties immersed in a constant D.C. magnetic field applied transversely across the main waveguide structure through which electromagnetic wave energy in the fundamental TE mode is propagated longitudinally. The associated transverse RF magnetic field component of the TE mode interacts with the constant D.C. magnetic field to create a magnetic RF component field in a longitudinal direction normal both to the RF magnetic field of the TE mode and the D.C. magnetic field. Since the longitudinal component of magnetic field comprises the RF magnetic field structure of the higher order TE mode, this mode will also be generated in the waveguide. It can thus be seen that the RF magnetic fields of both modes are normal to each other and mutually normal to the D.C. constant magnetic field H. As a result, both the dominant TE mode and the higher order TE mode will be propagated simultaneously through the waveguide structure beyond the ferrite ele ment. The degree of conversion from the dominant mode IB to the first higher order mode TE may be controlled by adjusting the value of the constant D.C. field. A portion of the energy in the fundamental or impressed mode may be taken ofi from the output of the waveguide in which it originated and energy in the converted first higher order TE mode is taken off through another port formed by a second rectangular waveguide which couples only to the first higher order TE mode. However, the second rectangular waveguide port is dimensioned such the TE mode coupled therein is converted at the output thereof to the fundamental or impressed TE mode. Such a device may be used to provide power dividing action in the manner to be described.

The various objects and features of the invention will be better understood from the following detailed description thereof when it is read in conjunction with the several figures of the accompanying drawing in which:

FIG. 1 shows a cross-sectional view of a mode converter embodying the invention;

FIGS. 2A and 23 respectively show diagrammatically field configurations of different modes applied to a rectangular waveguide, conversion between which may be accomplished by the wave converter of FIG. 1; and

FIG. 3 shows an electronically controlled power divider, utilizing the mode converter of FIG. 1, embodying the invention.

As shown in the cross-sectional view of FIG. 1, the mode converter comprises a section 1 of rectangular waveguide having transverse dimensions a and b, with capacitive ridge members 2 respectively attached to the I wide faces of the Waveguide section at a centrally-located point, and a slab or rod 3 of ferrite or other semiconductive or insulating material having gyromagnetic properties connected transversely across the waveguide between the ridge members 2. The broad dimension a of the waveguide section 1 is made sufliciently great to make the section support longitudinal propagation of both the aforementioned TE and TE modes, the field configurations of which applied to a rectangular waveguide are diagrammed in FIGS. 2A and 23, respectively. The dimensions of the capacitive ridge members 2 are made such as to provide equal phase propagation velocities to the TE and TE modes. It is preferred that the gyromagnetic slab or rod 3 be symmetrically positioned with respect to the narrow end wails of waveguide section 1. A constant magnetic fieid H is applied transversely to the ferromagnetic material 3 by any suitable means.

Microwave energy in one of two orthogonal modes, say the fundamental TE mode, is impressed on an input port of the waveguide section Land is propagated longitudinally thereover to the gyromagnetic device 3. Due to the'cross coupling between the RF magnetic fields mutually normal to the constant magnetic field, longitudinal magnetic field components will be generated by the device 3 in the waveguide to convert electromagnetic energy to the TE mode along the structure of the mode converter. The conversion may be made partial or com plete depending upon the intensity of the constant magnetic field applied to gyromagnetic element 3-. Thus the energy beyond the gyromagnetic slab 3 will comprise both the dominant TE mode and the first higher order TE mode.

The mode converter of FIG. 1 forms the basic element for an electronically-controlled power divider shown in FIG. 3. 'This power divider comprises two end dominant mode rectangular waveguide sections or ports 4 and 5 of such dimensions as to support the dominant TE mode, two other rectangular waveguide sections '6 and 7 having dimensions such as to support both the TE and the first higher order TE modes coupled respectively to the ports 4 and 5 by tapered low-reflection rectangular coupling waveguide sections 8 and 9, and an intermediate conversion device 10 connected between waveguide sections 8 and 9 which includes the slab or rod 3 of gyromagnetic material connected between the centrally located ridge sections 2 and subjected to a transversely applied constant magnetic field H. A branch rectangular waveguide section 11 is suitably oriented to couple only to the TE mode in' section 9 but is dimensioned so 'as to support only the dominant TE mode and thereby provide only the TE mode at the output thereof. As shown, Waveguide section 11 is substantially at the center of waveguide section 9 with its broad Walls parallel to the longitudinal magnetic RF field of the TE mode and is orthogonally positioned relative to waveguide sections 9 and 10. By this arrangement, the broad walls of waveguide 11 are orthogonal to' the RF magnetic component of fundamental TE mode. Inasmuch as the waveguide 11 is dimensioned to support only the 'I'E mode, the TE mode coupled from branch 9 to waveguide 11 will be converted therein to the TE mode so that only the fundamental TE mode is available at the output of waveguide 11.

In operation, microwave energy in the TE mode is impressed on the input of the waveguide section 4 and is propagated longitudinally thereover through sections 8, 6 and 10 to the gyromagnetic device 3 which converts it partially to the first higher order TE mode depending on the intensity H of the applied constant magnetic field which may be controlled electronically or by' other suitable me ans. The converted higher order TE mode energy and the energy remaining in the dominant TE modeare simultaneously propagated in section 1! beyond verted to the dominant TE mode as it passes through Waveguide section 11 and, as a result, the output from branch Waveguide 11 comprises the dominant TE mode. It is to be understood, of course, that the microwave frequency at the output of waveguide 11 is the same microwave frequency as that derived from port 5.

By means of the structure shown in FIG. 3, power limiting can also be obtained. The power limiting occurs because above a certain power level, which may be called the threshold level, the transferof energy between normal magnetic fields ceases to be orderly and, in fact, for input field increasing above thethreshold level, the transfer, in many cases, remains almost constant. Then, the power transferred is limited to this threshold level.

Although the application of a mode converter for converting between the TE and TE modes in rectangular waveguides has been illustrated and described, the same techniques can be used to convert between other nondegenerate orthogonal modes in rectangular waveguides. Other modifications within the spirit and scope of the invention illustrated and described will occur to persons skilled in the art.

What is claimed is:

1. A microwave frequency power dividing circuit comprising a hollow-pipe waveguide having a member eX- hibiting gyromagnetic properties disposed centrally therein, said waveguide being dimensioned so as to propagate electromagnetic wave energy at a prescribed frequency in both the dominant mode and the first higher order mode thereof, means for applying a unidirectional magnetic field of constant value transversely to said gyromagnetic member, means for propagating said dominant mode energy through one end of said waveguide with the electric energy component thereof parallel to said constant magnetic field, said gyromagnetic member interacting with said dominant mode energy to convert a portion thereof to said first higher order mode, both of said modes being simultaneously propagated through said hollow-pipe waveguide to the other end thereof, the magnetic components of said propagated modes being normal to each other and mutually normal to said constant magnetic field, waveguide means having its input coupled only to said first higher order mode energy and dimensioned such that the first higher order mode energy coupled thereto is converted to said dominant mode at the output of said Waveguide means, and means for deriving only said dominant mode at said other end of said hollow-pipe waveguide.

2. The microwave power dividing circuit in accordance with claim 1 in which said hollow pipe waveguide is a section rectangular in cross-section and dimensioned to support electromagnetic energy in the TE and'TE modes of a prescribed frequency, said gyromagnetic member being symmetrically positioned with respect to the narrow walls of said hollow-pipe waveguide and supported between capacitive ridge members attached to the broad walls of said hollow-pipe waveguide, said capacitive ridge rnembers being dimensioned to provide equal phase propagation velocities to said 'IE and TE modes.

3. A microwave frequency power dividing circuit comprising a first rectangular waveguide having a member exhibiting gyromagnetic properties disposed centrally therein, said waveguide being dimensioned so as to propagate electromagnetic energy at a prescribed microwave frequency in both the dominant mode and the first higher order mode thereof, means for applying a unidirectional magnetic field of constant value transversely to said gyromagnetic member, means for propagating said dominant mode energy through one end of said first waveguide with the electric energy component thereof parallel to said constant magnetic field, said gyrornagnetic member interacting with said dominant mode energy to convert a portion thereof to said first higher order mode energy, both of said modes being simultaneously propagated through said first waveguide to the other end thereof, the magnetic components of said propagated modes being normal to each other and mutually normal to said constant magnetic field, an output rectangular waveguide section dimensioned so as to propagate only said dominant mode energy, a tapered rectangular waveguide section interconnecting the other end of said first waveguide section and said output rectangular waveguide section, and a second rectangular waveguide coupled to a broad surface of said tapered waveguide section and having its longitudinal axis orthogonal to the longitudinal axis of said tapered waveguide section and its broad walls parallel to the magnetic component of said first higher order mode energy whereby only the first higher order mode is coupled to said second rectangular waveguide, said second rectangular waveguide being dimensioned to convert said coupled second higher order mode energy to said dominant mode which is taken off at the port formed by the end of said second rectangular waveguide.

4. A microwave power dividing circuit comprising an intermediate mode conversion device consisting of a section of rectangular hollow-pipe waveguide dimensioned to support longitudinal propagation therethrough of electromagnetic wave energy in both the dominant mode and the first higher order mode of a prescribed microwave frequency; two centrally-located capactive ridge members respectively attached to the wider internal faces of said waveguide section and dimensioned to give equal phase propagation velocity to said two modes; a gyromagnetic member connected between said capacitive ridge members and means for applying a transverse unidirectional magnetic field of a constant value to said gyromagnetic member; a tapered non-reflective rectangular waveguide section coupled to each end of said mode conversion section; a respective input and a first output rectangular waveguide section, each having cross-sectional dimensions such as to support only said dominant mode, coupled to a different one of said tapered waveguide sections, said tapered rectangular sections, said input and said first output rectangular waveguide sections and said rectangular waveguide conversion section being aligned along the same longitudinal axis; means for applying electromagnetic energy in said dominant mode through said input rectangular Waveguide section and one of said tapered sections to said gyromagnetic member, said gyromagnetic member interacting with said dominant mode to convert a portion thereof to said first higher order mode, both of said modes being simultaneously propagated through the other tapered waveguide section, the magnetic components of said propagated modes being normal to each other and mutually normal to said constant magnetic field; a second output rectangular waveguide coupled to said other tapered waveguide section and having its longitudinal axis orthogonal to the longitudinal axis of said other tapered rectangular section and oriented such that only the first higher order mode energy is coupled to said second output rectangular waveguide, the dimension thereof being such that the first higher order mode energy coupled thereto is converted to said dominant mode which is taken off at a port formed by the end of said second output rectangular waveguide; the dominant mode in said other tapered rectangular waveguide section being cou pled to said first output rectangular waveguide section.

No references cited. 

